JP3304340B2 - Receiver using spread spectrum - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a receiving apparatus using spread spectrum, and more particularly to a structure for preventing malfunction.

[0002]

2. Description of the Related Art In communication by spread spectrum, an information signal to be transmitted is spread-modulated with a specific code and transmitted, and a receiving side receives this signal and despreads using the same code to obtain an information signal. Such spread spectrum communication is excellent in secrecy and has a function of eliminating various kinds of interference waves and noise.

FIG. 6 is a block diagram of a conventional spread spectrum receiving apparatus. The communication signal emitted by the transmitting device is received by the antenna 44. This communication signal is spread-modulated by the M-sequence in the transmitting device. The outline of the spread modulation will be described.

FIG. 3A shows an information signal to be communicated, and FIG.
Indicates the M sequence. The transmitting device obtains the signal shown in FIG. 3C by multiplying the information signal in FIG. 3A by the M sequence (FIG. 3B).
In this example, the signal of FIG. 3C is obtained by keeping the M sequence as it is for the H level information signal and inverting the M sequence for the L level information signal. And this FIG.
The carrier wave (FIG. 3D) is modulated by the signal C to generate the communication signal of FIG. 3E. This communication signal is received by the antenna 44 of the receiving device.

A communication signal is first amplified by an auto gain control (AGC) 42 shown in FIG. This AGC42
Is designed to feed back the degree of amplification according to the output signal of the detector 20. AGC
The communication signal amplified by 42 is taken into the multiplying circuit 6. The multiplying circuit 6 is also provided with a reference M sequence for despreading the communication signal and reproducing information.

The reference M-sequence is generated by the M-sequence generator 4, and the same M-sequence (FIG. 3B) as the M-sequence used on the transmitting side is generated in order to properly reproduce information. The M-sequence generator 4 generates a reference M-sequence according to the oscillation signal from the VCO 2.

Here, even if the same reference M sequence as the M sequence used on the transmitting side is generated, information is not accurately reproduced unless the generation of the M sequence is synchronized with the communication signal. The switch 46 is connected to a reference power supply on the terminal b side and takes in an initial voltage. An oscillation signal is generated from the VCO 2 at a constant cycle, and the reference M sequence is also output from the M sequence generator 4 at a constant cycle.

[0008] The multiplication circuit 6 multiplies the communication signal by the reference M-sequence, and when the phases match, a signal as shown in FIG. 3F is output. That is, the information signal (FIG. 3)
A) is obtained by multiplying A) by the carrier waveform signal (FIG. 3D). If the communication signal and the reference M-sequence are out of phase and do not match, the signal of FIG. 3F cannot be obtained.

The signal shown in FIG. 3F is a band-pass filter (B
PF) 12, where the frequency component of the carrier is extracted, and the information is reproduced through an information demodulation circuit 18. 4A shows the frequency spectrum of the signal of FIG. 3F, and FIG. 4B shows the frequency spectrum of the signal of FIG. 3E. FIG. 4 shows a case where the phase of the communication signal matches the phase of the reference M sequence.
The frequency spectrum of A can be obtained. If the phases do not match, the frequency spectrum is almost the same as in FIG. 4B.

By the way, in order to accurately reproduce information, it is necessary to match the phase of the M-sequence on the transmitting device side with the phase of the M-sequence generated on the receiving device side. For this reason, a point in time when the phases of both fluctuating coincide with each other is detected, and based on this detection, the reference M sequence is generated following the phase of the communication signal thereafter. The specific configuration is shown below.

The detector 20 takes in the signal from the BPF 12, extracts the envelope of the waveform, and outputs it. As described above, since the BPF 12 extracts only the frequency component N (FIG. 4) of the carrier, if the phase of the communication signal and the reference M sequence match (FIG. 4A), a large waveform as shown in FIG. Is output, and an envelope K1 can be obtained. On the other hand, when the phases of the communication signal and the reference M sequence do not match (FIG. 4B), a small waveform is output as shown in FIG.
An envelope K2 is obtained.

The output signal from the detector 20 is as follows:
It is periodically integrated by the integration dump 34. Thereafter, the comparator 36 determines whether or not the integrated value exceeds a predetermined threshold. That is, when the phase of the communication signal matches the phase of the reference M sequence, a large envelope K1 is output and exceeds the threshold value. Therefore, the comparator 36 recognizes that the phase of the communication signal matches the phase of the reference M sequence, Outputs a judgment signal.

In order to prevent erroneous determination, the synchronization determination circuit 38 outputs a switching signal only when the reference coincidence signal is given twice consecutively. In response to this switching signal, the switch 46 switches from the reference power supply at the terminal b to the terminal a. Thereafter, the VCO 2 generates an oscillation signal based on the control signal given from the terminal a, and the M-sequence generator 4 generates a reference M-sequence in a cycle following the phase of the communication signal.

The contents of the control signal supplied from the terminal a will be described below. The communication signal having passed through the AGC 42 is also supplied to a multiplier 8 as a first coincidence detection circuit and a multiplier 10 as a second coincidence detection circuit.

The multiplier 8 is provided with an output delayed by one cycle from the reference M sequence together with the communication signal. FIG. 5A
Is an output signal R5 based on the reference M sequence, and FIG. 5B is a waveform of the output signal S5 from the multiplier 8. Output signal S5
Is shifted by one period from the position F of the synchronized reference M sequence. Further, the M sequence advanced by one cycle is provided to the multiplier 10. FIG. 5C shows an output signal U5 from the multiplier 10.

Each of these output signals is supplied to a BPF 1
The signals are supplied to an adder 50 via the detectors 4 and 16 and the detectors 22 and 24. Output signal S5 is provided to an addition input of adder 50, and output signal U5 is provided to a subtraction input. That is,
The output signal U5 is set to a negative value and is added to the output signal S5. FIG. 5D shows an output signal from the adder 50, which is guided to the terminal a via the loop filter 40.

As described above, the switch 46 switches to the terminal a when the phase of the communication signal matches the phase of the reference M sequence. Therefore, the control voltage of VCO2 is controlled according to the slope portion V5 of the output signal in FIG. 5D, and an oscillation signal is generated from VCO2 at a timing following the phase of the communication signal. Therefore, the reference M sequence generated by the M sequence generator 4 is also generated in synchronization with the phase of the communication signal, and accurate information is reproduced.

[0018]

The above-mentioned conventional spread spectrum receiving apparatus has the following problems. A
The GC 42 is configured to feed back the degree of amplification according to the output signal of the detector 20. That is, when no signal is received, the AGC4
The amplification degree of No. 2 is the maximum state.

Therefore, when the antenna 44 suddenly receives a signal in this state, the detector 20 outputs an output signal W of large noise as shown in FIG. 5E. Then, when the threshold value L in the comparator 36 is exceeded, the synchronization determination circuit 38
Will output a switching signal.

When a signal is suddenly given, AGC
42 attempts to keep the amplitude constant. For this reason, once an erroneous determination occurs, the switch 46 remains switched to the terminal a, and it is impossible to escape from the erroneous determination state.

It is an object of the present invention to provide a receiving apparatus using spread spectrum which does not cause a malfunction even when a strong noise is generated due to a sudden signal input or the like.

[0022]

According to a first aspect of the present invention, a spread spectrum receiving apparatus outputs an oscillation signal in accordance with a received initial voltage, fetches a control signal when a switching signal is given, and receives the control signal. A voltage-controlled oscillation circuit that outputs an oscillation signal according to a voltage, a reference pseudo-noise code generation circuit that generates a reference pseudo-noise code based on an oscillation signal from the voltage-controlled oscillation circuit, and a transmission device that is spread-modulated by the pseudo-noise code. Receiving a communication signal, collating the reference pseudo-noise code with the communication signal, and outputting a reference coincidence signal when they match, a reference control circuit that outputs the switching signal based on the reference coincidence signal,
A first pseudo-noise code generating circuit for generating a first pseudo-noise code delayed by a predetermined period with respect to the reference pseudo-noise code, receiving a communication signal from a transmitting apparatus spread-modulated by the pseudo-noise code; A first coincidence detection circuit for comparing the pseudo-noise code of the first embodiment with the communication signal to output a first coincidence signal, and generating a second pseudo-noise code advanced by a predetermined period with respect to the reference pseudo-noise code. A second pseudo-noise code generating circuit, which receives a communication signal from a transmission device spread-modulated by the pseudo-noise code, compares the second pseudo-noise code with the communication signal, and outputs a second coincidence signal. 2, the one of the first coincidence signal and the second coincidence signal is set to a negative value and added to the other signal to generate a control signal. Output with an adder circuit In the receiving apparatus by diffusion,
An output signal of the first match detection circuit and a second match detection circuit
Generates a signal to cancel noise from the road output signal
The switching control circuit matches the generated signal with the reference.
A switching signal is output based on the output signal of the detection circuit.
That, it is characterized in that.

According to a second aspect of the present invention, there is provided a receiving apparatus using spread spectrum according to the first aspect, wherein the output signal of the first coincidence detecting circuit and the second coincidence signal are output.
An arithmetic circuit for adding and subtracting the output signal of the detection circuit to calculate and output an average signal by halving the output signal; and the switching control circuit outputs a switching signal based on the output signal of the reference match detection circuit and the average signal. It is characterized by

[0024]

According to the first aspect of the present invention, the output signal of the first coincidence detecting circuit and the second signal are output.
To cancel noise from the output signal of the match detection circuit
The switching control circuit generates a signal, and the generated signal
Switching signal based on the output signal of the reference match detection circuit
Is output.

In the receiving apparatus according to the second aspect of the present invention, the arithmetic circuit includes an output of the first coincidence detecting circuit.
Summing the input signal and the output signal of the second coincidence detection circuit ,
The average signal is calculated by halving and output. Then, the switching control circuit outputs a switching signal based on the output signal and the average signal of the reference match detection circuit .

Therefore, in the receiving apparatus based on the spread spectrum according to the first and second aspects, even when a strong noise is generated due to a sudden signal input or the like, the output signal of the reference coincidence detecting circuit is averaged. The signals do not cancel each other and the switching signal is not output erroneously.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a receiving apparatus using spread spectrum according to the present invention will be described. FIG. 1 shows a block diagram in the present embodiment. The communication signal emitted by the transmitting device (not shown) is received by the antenna 44. This communication signal is spread-modulated by the M sequence (FIG. 3B) as a pseudo-noise code in the transmission device (see FIG. 3E).

The received communication signal is first amplified by an automatic gain control (AGC) 42. This AGC
Reference numeral 42 is such that the degree of amplification is fed back according to the output signal of the detector 20.

The communication signal amplified by the AGC 42 is taken into the multiplier 6. This multiplication circuit 6 includes:
In order to reproduce information by despreading a communication signal, a reference M sequence as a reference pseudo noise code is also provided. The reference M-sequence is generated by an M-sequence generator 4 which is a pseudo-noise code generator, and the same M-sequence used on the transmission side (FIG. 3B) is generated in order to properly reproduce information. ing. The M-sequence generator 4 generates a reference M-sequence in accordance with an oscillation signal from the VCO 2 that is a voltage-controlled oscillation circuit.

Here, even if the same reference M-sequence as the M-sequence used on the transmitting side is generated, the information is not accurately reproduced unless the M-sequence generation is synchronized with the phase of the communication signal. The switch 46 is connected to a reference power supply on the terminal b side and takes in an initial voltage. An oscillation signal is generated from the VCO 2 at a constant cycle, and the reference M sequence is also output from the M sequence generator 4 at a constant cycle.

When the phase of the reference M sequence matches the communication signal, a high frequency signal is output from the multiplier 6 which is a reference match detection circuit (see FIG. 4A). Is output (see FIG. 4B). The band-pass filter (BPF) 12 receives the signal from the multiplier 6, and receives the carrier frequency component N (FIG. 4).
Extract and output only. Then, the information is reproduced through the information demodulation circuit 18. By the way, in order to accurately reproduce information, it is necessary to match the phase of the M-sequence on the transmitting device side with the phase of the M-sequence generated on the receiving device side. For this reason, a point in time when the phases of both fluctuating coincide with each other is detected, and based on this detection, the reference M sequence is generated following the phase of the communication signal thereafter. The specific configuration is shown below.

The communication signal passed through the AGC 42 is supplied to the multiplier 8
It is also given to 10. The multiplier 8 includes a first M sequence (first sequence) delayed by a half cycle with respect to the reference M sequence together with the communication signal.
Pseudo-noise code). FIG. 2A shows the output signal R1 based on the reference M sequence, and FIG. 2B shows the waveform of the output signal S1 from the multiplier 8. The output signal S1 is shifted by a half cycle from the position F of the synchronized reference M sequence. Also, a second M sequence advanced by a half cycle (second pseudo noise code)
Is provided to the multiplier 10. FIG. 2C shows the multiplier 10
Is an output signal U1.

The output signals S1 and U1 output from the multipliers 8 and 10 are output from the BPFs 14 and 16 and the detector 2 respectively.
The signals are supplied to the adder 28 via 2, 24. Then, here, both signals are added, and are taken into the divider 32 and 1 /
2 signal. That is, the output signals S1 and U1 are averaged and output as an average signal Q1 shown in FIG. 2D. This average signal Q1 is provided to a subtraction input of the adder 26.
On the other hand, the output signal R1 (FIG. 2A) from the detector 20 is given to the addition input of the adder 26, and is subtracted from the average signal Q1. When the output signal R1 is a, the output signal S1 is b, and the output signal U1 is c, the output signal from the adder 26 is represented by the following equation (1).

[0034]

(Equation 1)

The waveform of the output signal from the adder 26 is shown in FIG.
Shown in When the phase of the communication signal matches the phase of the reference M sequence,
The output signal of FIG. 2E is obtained, is periodically integrated by the integration dump 34, and accumulates a signal for one cycle of the M sequence.
Thereafter, the comparator 36 recognizes that the predetermined threshold value L is exceeded, and the comparator 36 outputs a determination signal to the synchronization determination circuit 38.

In order to prevent erroneous determination, the synchronization determination circuit 38 outputs a switching signal only when the reference coincidence signal is given twice consecutively. In response to this switching signal, the switch 46 switches from the reference power supply at the terminal b to the terminal a. A control signal is supplied to this terminal a via a loop filter 40. The control signal is supplied to the adder 30
, The output signal U1 is set to a negative value and the output signal S
This is a signal that is added to 1 and output (see FIG. 5D).

After the switching of the switch 46, the VCO 2 generates an oscillation signal based on this control signal, and the M sequence generator 4 generates a reference M sequence at a period following the phase of the communication signal. Therefore, the communication signal and the phase of the reference M-sequence generated from the M-sequence generator 4 are reliably synchronized, and accurate information is reproduced.

By the way, when a signal is suddenly applied to the receiving apparatus, a large noise is generated. In particular, AGC
Reference numeral 42 indicates that the degree of amplification is fed back according to the output signal of the detector 20. When no signal is received, the degree of amplification of the AGC 42 is at the maximum. For this reason, if the antenna 44 receives a signal abruptly in this state, the detectors 20, 22, and 24 output the noise output signals R shown in FIGS. 2A, 2B, and 2C, respectively.
2, S2 and U2 are output.

However, in the present embodiment, the comparator 36 determines whether or not the signal calculated by the above equation 1 exceeds a threshold, and outputs a determination signal. As shown in FIGS. 2A, 2B and 2C, the noise output signal R
2, S2 and U2 occur simultaneously. Therefore, according to the equation (1), the noise output signal R2 becomes the output signal S2, U2
And the adder 26 does not output a signal corresponding to this noise (see FIG. 2E).

Therefore, erroneous determination of phase coincidence between the communication signal and the reference M sequence can be easily and reliably prevented. In addition, it is possible to easily escape from the erroneous determination state. In the above embodiment, the multipliers 8 and 10 include:
A first M sequence delayed by a half cycle with respect to the reference M sequence and a second M sequence advanced by a half cycle with respect to the reference M sequence are provided.
However, the present invention is not limited to this half cycle, and a larger or smaller cycle may be set.

[0041]

According to the first aspect of the present invention, the output signal of the first coincidence detecting circuit and the output signal of the first coincidence detecting circuit are provided.
And noise from the output signal of the second match detection circuit
The switching control circuit generates a signal for the
Based on the detected signal and the output signal of the reference match detection circuit
Output signal.

In the receiver according to the second aspect of the present invention, the arithmetic circuit includes an output of the first coincidence detecting circuit.
Summing the input signal and the output signal of the second coincidence detection circuit ,
The average signal is calculated by halving and output. Then, the switching control circuit outputs a switching signal based on the output signal and the average signal of the reference match detection circuit .

That is, in the receiving apparatus based on the spread spectrum according to the first and second aspects, even when a strong noise is generated due to, for example, a sudden signal input or the like, the output signal of the reference coincidence detecting circuit is averaged. The signals do not cancel each other and the switching signal is not output erroneously.

Therefore, malfunction of the device can be reliably prevented.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a receiving apparatus using spread spectrum according to the present invention.

FIG. 2 is a diagram showing output signals from respective detectors and the like in the receiving device of FIG. 1;

FIG. 3 is a waveform diagram for explaining a communication system using spread spectrum.

FIG. 4 is a frequency spectrum corresponding to the waveforms of FIGS. 3F and 3E.

FIG. 5 is a diagram showing various coincidence signals in the conventional receiver of FIG. 6;

FIG. 6 is a block diagram showing a conventional spread spectrum receiving apparatus.

[Explanation of symbols]

 ... VCO 4... M-sequence generator 6, 8, 10... ·············································· Switch

──────────────────────────────────────────────────続 き Continuation of front page (56) References JP-A-62-139424 (JP, A) JP-A-2-11034 (JP, A) JP-A-3-236645 (JP, A) JP-A-3- 236646 (JP, A) JP-A-2-75238 (JP, A) JP-A-58-141050 (JP, A) JP-A-58-141049 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04J 13/00-13/06 H04B 1/69-1/713

Claims (2)

(57) [Claims] 1. A voltage-controlled oscillation circuit for outputting an oscillation signal according to a received initial voltage, taking in a control signal when a switching signal is given, and outputting an oscillation signal in accordance with the voltage of the control signal. A reference pseudo-noise code generation circuit that generates a reference pseudo-noise code based on an oscillation signal from the circuit, receives a communication signal from a transmitting device that is spread-modulated by the pseudo-noise code, and compares the reference pseudo-noise code with the communication signal And a reference coincidence detection circuit for outputting a reference coincidence signal when they match, a switching control circuit for outputting the switching signal based on the reference coincidence signal, a first pseudo noise delayed by a predetermined period with respect to a reference pseudo noise code A first pseudo-noise code generating circuit for generating a code, receiving a communication signal from a transmitting apparatus spread and modulated by the pseudo-noise code, and A first coincidence detection circuit for comparing a code with a communication signal and outputting a first coincidence signal; a second pseudo-noise code for generating a second pseudo-noise code advanced by a predetermined period with respect to the reference pseudo-noise code A noise code generation circuit, a second coincidence for receiving a communication signal from a transmitting device spread-modulated by the pseudo noise code, collating the second pseudo noise code with the communication signal, and outputting a second coincidence signal A detection circuit that sets one of the first coincidence signal and the second coincidence signal to a negative value, adds the other signal to the signal, generates a control signal, and outputs the control signal to the voltage-controlled oscillation circuit. An output signal of the first coincidence detection circuit and a second coincidence detection circuit.
Generates a signal to cancel noise from the road output signal
The switching control circuit matches the generated signal with the reference.
A switching signal is output based on the output signal of the detection circuit.
That, the receiver according to the spread spectrum, characterized in that. 2. An apparatus according to claim 1, wherein the output signal of the first coincidence detecting circuit and the second coincidence detecting circuit are output.
The output signal of the road is added and the average signal is calculated by halving,
A receiving circuit based on spread spectrum, comprising: an arithmetic circuit for outputting a signal; and the switching control circuit outputs a switching signal based on an output signal and an average signal of the reference coincidence detecting circuit .